Spark plug



June 8, 1948.

H. W AN DERSEN SPARK PLUG Filed June ll, 1946 s ##VZWA..

Patented June 8, 1948 UNITED STATES PATENT OFFICE SPARK PLUG Harold W. Andersen, Bayside, N. Y.

Application June 11, 1946, Serial No. .675,881

This invention relates to a spark plug, of the type adapted for use in internal combustion engines.

An object of the invention is to provide such a plug in which an intensifier or booster gap is open during operation at low temperatures and is automatically short c-ircuited just before the engine and plug reach their normal higher operating temperature.

Another object is to provide a condenser which acts when the intensifier gap is open to strengthen the Kdischarge across said gap.

A further object is'to Vprovide certain improvements in the form, construction and arrangement of the parts whereby the above named and other objects may be effectively attained.

A practical embodiment of the invention is shown in the accompanying drawings, in which Fig. 1 represents a vertical axial section through the spark plug, and

Fig. 2 represents a detail vertical axial section showing certain of the parts on a larger scale.

Referring to the drawings, the lower part of the plug is conventional and includes the base I, externally threaded at 2 and provided with an internal shoulder 3 on which the matching shoulder of the porcelain 4 is supported through the intermediary of the annular gasket 5. The gland nut 6 screws into the top of the base at 'I and completes the seal by engagement with the gasket 8. An electrode 9 is welded on the bottom of the base I, and the center electrode I passes axially through the lower part of the porcelain and is secured to the bushing I I which is screwed and cemented tightly into the threaded recess I2.

The upper part of the porcelain contains a cylindricalV bore I3, the upper end of which is enlarged and threaded as shown at I4 to receive the metallic crown I5. This crown is roughly cup-shaped, with a hole I6 in its middle, shoulders l1 and l8 near its top, and Vent holes I9 in its sides. The shoulder I'I is designed to support the periphery of a bi-metallic snap disc 20, which may have a wear-resistant contact piece 2I mounted at its center, and a packing or retaining ring 22 overlies the periphery of the disc but Without binding against it. The shoulder I8 supports the base of the terminal connector 23, and the top edge of the crown I is spun over as shown at 24 to grip iirmly the base of the connector. The vertical distance between the shoulders I'I and I8 is approximately equal to the diameter of the ring 22 plus the terminates .below the hole I6. For clearness of illustration the parts 25, 26 and 2l are shown in the drawings as being slightly spaced, but it will be understood that they may, in practice, be closely nested together,

The fuel ignition spark gap is between the electrodes 9 and I0, which may be of any specific form desired, and an intensifier gap is formed at the point Where the electrode k2li passes through the 'hole I6. When the disc 26 is in its upper (cold) position the ignition current flows through the connector 23 and crown I5, across the intensifier gap to electrode 26, down through bushing II and electrode I0, across the ignition gap to electrode 9, and thence to ground through the base I. Before jumping the intensifier gap each current impulse builds up a strong tension between the tube 25 and electrode 26 which, with the insulating tube 21, constitute a condenser with appreciable capacity, so that the spark which jumps the intensifier gap is materially reinforced and ensures a correspondingly strong or hot spark at the ignition gap.

The bi-metallio disc 20 is formed, in a known manner, of superimposed discs of metals having different coeicients of expansion and slightly dished, so that it is convex upwardly at low temperatures (as shown in full lines) but will snap to the position shown in broken lines (convex downwardly) as the temperature rises past a predetermined point. When the disc thus snaps to its lower (hot) position it immediately shorts out the intensifier gap and permits the current to flow from the connector 23, through the disc; 2B and contact piece 2l to the electrode 26, the top of this electrode being so positioned as to: assure the formation of a good contact. Na turally, when the temperature of the disc is again reduced it will snap back to its upper position, where it is spaced from the electrode 26 by a. greater dista-nce than that between said electrode and the walls of the hole I6. The action of the snap disc may be explained in more detail by' thickness of the disc, so that the periphery of u noting that it tendstoflatten out with an increase 3 of temperature, for instance in the range from 100 to 140 F., and at a certain point it brings the contact piece 2l closer to the end of electrode 2B than the distance across the intensier gap. When this occurs the spark jumps between the 5 piece 2| and the electrode (instead of across the gap), causing a sharp additional rise in temperature of the disc past the snapping point, so that the contact between the piece 2| and the electrode is immediately closed, as setifrth above.

Therei'is thus provided an intensifier'gapI-of unvarying size and strong action, which is never closed but is instantaneously shorted ,out Whenthe engine in which the plug is mounted reaches Y a temperature at which an intensified spark is 15 no longer needed. The surfaces ofthe parts-zoonstituting the intensifier gap need-notfbecylin.- drical and concentric but may, ifV desired.' b shaped to provide one or more definitely` lcalied gaps. The insulating tube 21 may be of any 20 suitable dielectric' materialr and I may.: inv some instances, be Wholly orfpartiallyfomitteif It'willbefunderstood that Ivarious changes may be maderin the-form, construction; arrangement andi-materials ofthe apparatus andin thefsteps 25- of-1 the methodV without departing from the spirit and'scope' of lthe invention; hence I do not 1intend tez-belh limited" to: thevemb'odinrients shovvnf.` and described;l but yWhat'l claim- 1is:

V 1.1' A spark plug-.of thecharacter described-com- 30 prising, anfelectrode;aconductive element' adjacenti'said. electrode and:spacedareddistance therefrom: to provide fan intensifier spark gap; and -ia separateheat-responsive elementin con-'- tinuo'usl-electrical iconnectionzwithasaidiiconduc; 35

ment adapted to snap substantially instantaneously between the positions named.

3. A spark plug according to claim 1 in which the heat-responsive element is a. loi-metallic snap disc. f

4. A spark plug according to claim 1 in which the conductive element surrounds the electrode at a fixed distance, and in which the heat-responsive element is movable into and out of contact Witlan'en'd vofthe electrode f axially with respect to saidf'el'e'ctrode.

5. A spark plug of the character described comprising, an electrode, a conductive element adjacent said electrode and spaced a Xed distance therefrom to provide an intensifier spark gap ya:separate heat-.responsive element' in continuous electrical connection with said conductive'elnientandadapted at low temperatures to assume'a position more distant from said electrode than the width offsaid gap and at normal engi-ne operating-Y temperatures tornake contact with` said.V electrode Vandal A conductive bodyf of extended area, said body being connected tothe conductive element, surrounding--said electrode and-.being dielectrically separated therefrom."

6. A |sparkplug accordingto claim'inwliich the conductive elementsurroundsytheelectrode and 'provides an annu-lar'sparkfgapyandlinwlich the heat-responsive element islmovableginto and :outvof contact Withanendl voffthe.- electrode axially with. respect -to saidelectrode.

REFERENCES jcrrnn' The following references are fof record: inthe le` -ofithis patent:` y

Urn'iizn'`V STATES PATENTS" Number Name Date f, 3 154830.31: Franzen:` Aug-T4; 1925 117045181" Aspden- 1 Mar- 1251929 

